Not very many. You'll really only need to do tipping to anyone off the ship, onboard mostly if you get room service or if you make use of the porters when disembarking. Everything onboard, including drinks, can be charged to the room, including gratuity. That's about the best I can answer without knowing more of who you intend to tip. The main tipping for the waitstaff and your room steward will be explained in the documentation when you get it.